1. Field of the Invention
This invention relates to acceleration accumulating chain conveyors used in assembly lines or the like, and more particularly, to an acceleration accumulating chain conveyor which accelerates articles to be conveyed more quickly from stopped positions, to shorten the conveying time.
2. Prior Art
Assembly lines are required to suppress noises caused by the travelling conveyor chains to the lowest levels possible. The only method known, until recently, to lower the noise was to run the chain more slowly. Unfortunately, the conveying speed of articles to be conveyed also becomes slower so that the efficiency of production is degraded. Further, when the articles to be conveyed are temporarily accumulated on the conveyor of the assembly line, the chain keeps travelling beneath the articles, which slide undesirably relative to the chain, often damaging the articles, the conveyor, or both. An acceleration accumulating chain conveyor which overcomes these problems is disclosed in U.S. Pat. No. 4,339,030, the teachings of which are fully incorporated herein by reference. As shown in FIG. 4 herein, a large diameter support roller is loosely fitted onto a conventional chain roller and the articles to be conveyed are mounted on the support roller. The rotation of the chain roller due to the travelling of the chain is transmitted to the support roller by the rotary frictional force between the chain roller and the support roller, so that the conveying speed of the articles becomes the chain speed plus the speed corresponding to the ratio of the radius of the support roller to the radius of the chain roller. Thus the articles are conveyed at a speed which is faster than the chain speed and, when the articles are accumulated during conveying, the conveying roller overcomes the rotary frictional force effecting engagement with the chain roller, and rotates backwards, in spite of the travelling of the chain and without any sliding of the article on or relative to the chain.
In such conveyors, when accumulated articles are released, the backwardly rotating support roller is again rotated forwardly by the rotary frictional force. The articles to be conveyed begin moving on the conveying rollers and eventually reach or reattain the regular conveying speed, which is faster than the chain speed. However, the frictional force between the support roller and chain roller is produced only because the inner peripheral surface of the cylindrical support roller and the outer peripheral surface of the cylindrical chain roller are urged and abut against each other. The rotary frictional force is thus so small that a significant time lag occurs between the release and subsequent attainment of the regular conveying speed of the articles. As the regular conveying speed of the articles cannot be attained at the same time as, or even soon after the articles are released, accumulation inevitably results in time delays, which slow conveying time, which in turn delay the entire production line. Even small delays have a substantial cumulative effect on production efficiency Accordingly, the solution of U.S. Pat. No. 4,339,030 itself presented a new problem.
This invention solves the new problem by increasing the rotary fictional force between the support rollers and the chain rollers, without hindering the reverse rotation of the support rollers, which enables accumulation of articles without damage from sliding engagement.